The increasing use of electronics for any of a variety of purposes has naturally resulted in an increase in their use in relatively cold environments. Such environments may be earthbound environments but more commonly may be airborne environments in connection with the operation of air or space craft.
Even though modern day electronic systems require but a minor fraction of the power required by vacuum tubes to operate, because of their compactness, relatively high heat densities attend their operation. The heat generated by such operation must be transferred away from the electronic components to prevent the same from overheating and suffering damage or destruction. Not uncommonly, the heat generated by such electronic components is absorbed by the vaporization of a refrigerant. In the usual case, the cooling system will include an evaporator in heat exchange relationship with the electronic components which constitute the heat load. The evaporator will have an inlet and an outlet with the outlet being connected to a compressor which compresses vaporized refrigerant and provides the same to a condenser whereat it is condensed. The condensed refrigerant is then conveyed to a receiver and from the receiver through an expansion valve to the inlet of the evaporator. Evaporation takes place within the evaporator with the heat of vaporization being added to the refrigerant by the heat from the load.
When the system is in continuous operation, no particular difficulties in maintaining the operation are encountered. However, when operation of the system is intermittent, difficulty may be encountered in attempting to start up the system when the same has been subjected to low temperatures for a sufficient period of time so as to reach approximate temperature equilibrium with the environment.
In such a case, at the low temperature of the environment, the vapor pressure of the refrigerant may be so low as to make the system incapable of start-up. For with very low pressures, there will be little driving force to force liquid refrigerant through the expansion valve and at the same time, there will be very little mass for the compressor to compress to generate a sufficient pressure differential for operation.
The present invention is directed to overcoming the above problem.